Mounting arrangement for cantilevered chair arm

ABSTRACT

A chair wherein each cantilevered side arm terminates in a base portion positioned adjacent the rear edge of the seat. This base portion has an armlike mounting portion projecting forwardly therefrom into the interior of the seat. A U-shaped tubular frame is positioned within the interior of the seat so that the legs of the U-shaped frame project forwardly of the seat, and the bight of the U-shaped frame is positioned adjacent the rearward edge of the seat. The U-shaped frame is fixedly secured to a conventional chair-control frame as disposed interiorly of the seat. The rear portion of the U-shaped frame, including the bight and the elbows which join the bight to the legs, is inclined upwardly and rearwardly relative to the legs. The armlike mounting portions, as they project forwardly into the chair seat, are inclined downwardly at a similar angle. An upwardly opening, channel-like bracket is fixedly secured to each of the elbows. Each bracket fixedly and snugly receives therein the armlike mounting portion. The mounting portion, bracket and U-shaped frame are suitably fixedly connected by threaded fasteners.

FIELD OF THE INVENTION

This invention relates to a chair having cantilevered side arms and, in particular, to an improved arrangement for fixedly mounting the side arms to structure which is disposed internally of the chair seat.

BACKGROUND OF THE INVENTION

Office chairs having side arms have conventionally employed a multiple post arrangement for mounting the side arm. This multiple post arrangement has generally been secured to structure disposed internally of the seat, with the multiple posts projecting outwardly from the side of the seat and upwardly for attachment to the side arm adjacent the front and rear ends thereof. This multiple post arrangement was generally considered necessary in order to provide the side arm with adequate strength, particularly so as to be capable of withstanding the substantial downwardly and sidewardly directed loads as imposed on the arm during use of the chair. While this type of side arm arrangement does normally provide adequate strength and durability, nevertheless it also greatly restricts the esthetics and design characteristics of the chair.

In an attempt to provide a chair having a substantially different appearance, several office chairs have been designed utilizing cantilevered side arms. That is, the front end of the arm is not supported, so that the side arm is fixedly supported in its entirety solely by fixedly anchoring the rear end of the arm to suitable structure stationarily associated with the chair. This thus makes it extremely difficult to provide a strong and secure mounting of the cantilevered side arm, particularly since the side arm must be capable of withstanding minimum loading standards relative to downward vertical loads and outward sidewardly directed loads. Providing a proper structural mounting of the cantilevered arm so as to comply with, or exceed, the minimum loading requirements has thus presented a substantial obstacle and, in many instances, has required that the design (that is, the esthetics) of the arm be modified or that complex and costly structures be utilized.

Accordingly, this invention relates to an office chair having side arms, specifically cantilevered side arms, and the purpose of this invention is to provide an improved mounting arrangement for the cantilevered side arms so as to provide the side arms with substantial strength and rigidity whereby the side arms are capable of withstanding imposition thereon of external loads of substantial magnitude when imposed vertically downwardly and horizontally outwardly sidewardly thereof, while at the same time this improved mounting arrangement does not interfere with the ornamental and design characteristics of the cantilevered arms and of the overall chair. The improved arm mounting arrangement of this invention also enables the cantilevered arms and mounting structure to be manufactured and assembled with minimal complexities so as to permit efficient and economical manufacture.

In the chair of this invention, each cantilevered side arm includes an arm rest portion which at its rearward end terminates in an intermediate arm portion which is of compound curvature in that it projects rearwardly, curves downwardly, and also curves inwardly so as to terminate in a base portion which is positioned adjacent the rear edge of the seat. This base portion has an armlike mounting portion integral therewith and projecting forwardly therefrom into the interior of the seat. This armlike mounting portion is cantilevered from the base portion. The mounting structure for the cantilevered arms includes a U-shaped tubular frame which is positioned within the interior of the seat so that the legs of the U-shaped frame project forwardly of the seat, and the bight of the U-shaped frame is positioned adjacent the rearward edge of the seat. The legs of the U-shaped frame are fixedly secured, as by screws, to the conventional chair-control frame as disposed interiorly of the seat. The rear portion of the U-shaped frame, including the bight and the curved elbows which join the bight to the legs, is disposed within a plane which is inclined upwardly and rearwardly relative to the legs, such as at an angle of approximately 30°. The armlike mounting portions, as they project forwardly into the chair seat, are also inclined downwardly at a similar angle. An upwardly opening, channel-like bracket is fixedly secured to each of the elbows, and is inclined at the same angle as the elbow. Each bracket fixedly and snugly receives therein the armlike mounting portion. The mounting portion, bracket and U-shaped frame are suitably fixedly connected by threaded fasteners.

The cantilevered arm mounting arrangement of this invention is such as to be cost effective, relative to both labor and materials. Further, this arrangement is capable of meeting industry standards by means of a structure which, when subjected to minimal loading requirements, does not provide any plastic yield or permanent deformation, while at the same time utilizing a simple connecting structure which requires only minimal tooling and which does not interfere with the shape or size or comfort of the chair seat.

Other objects and purposes of the invention will be apparent to persons familiar with chairs of this type upon reading the following specification and inspecting the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a chair employing cantilevered side arms according to this invention.

FIG. 2 is a plan view of the chair seat, with the cushion and internal shell removed, so as to illustrate the attachment of the arm mounting structure to the chair-control frame.

FIG. 3 is a side view of the structure illustrated in FIG. 2 but showing the inner shell in cross section.

FIGS. 4, 5 and 6 are respectively top, side and rear views of the cantilevered arm.

FIG. 7 is a side view of the arm mounting structure which is disposed interiorly of the chair seat.

FIGS. 8 and 9 are fragmentary views taken substantially along lines VIII--VIII and IX--IX, respectively, as appearing in FIG. 7.

FIG. 10 is a side view similar to FIG. 7 but showing the attachment of the cantilevered arm to the mounting structure.

FIG. 11 corresponds to FIG. 9 but shows the arm secured to the bracket, and is hence taken substantially along line XI--XI in FIG. 10.

FIGS. 12 and 13 are sectional views taken substantially along lines XII--XII and XIII--XIII, respectively, as appearing in FIG. 11.

Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, the words "upwardly", "downwardly", "leftwardly" and "rightwardly" will refer to directions in the drawings to which reference is made. These same terms will also have reference to the normal vertical and horizontal orientation of the chair. The words "front" and "rear" will be used in their conventional sense to make reference to the front and rear edges of the chair and designated parts thereof. The words "inwardly" and "outwardly" will refer to directions toward and away from, respectively, the geometric center of the chair and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.

DETAILED DESCRIPTION

FIGS. 1-3 illustrate an office-type chair 10 having a back assembly 11, a seat assembly 12 and a pedestal-type base 13. The seat assembly has, in the interior thereof, a chair control 16 which fixedly supports thereon the inner seat shell 17, the latter being suitably covered and surrounded by an upholstered cushion 18. A suitable outer or lower shell 19 encloses the lower portion of the seat assembly.

The chair control 16, in the illustrated embodiment, is of the conventional tilt-type for permitting tilting of the seat relative to the pedestal. This conventional chair control includes, as illustrated in FIGS. 2 and 3, a rigid support frame which includes a pair of parallel and approximately horizontally extending rails 21, which rails have hubs 22 fixed thereto. These hubs are anchored to the ends of an elongated torsion bar 23, which bar in turn is anchored to suitable side brackets 24 which are fixed to opposite ends of a cross channel 26. The latter has a suitable bearing 27 mounted thereon for being fixedly attached to the upper end of the conventional threaded spindle (not shown) which vertically joins the seat assembly and the base. The chair control 16 is conventional, although it may assume many different configurations, examples of such controls being illustrated by U.S. Pat. Nos. 4,067,610 and 4,219,233. Such controls all conventionally provide a support frame which typically includes a pair of support elements equivalent to the rails 21, for attachment to the inner shell, so that further description of the chair control is believed unnecessary since such controls are well understood by those in the chair industry.

The chair of this invention is provided with a pair of cantilevered side arms 28 and 29, which arms are suitably fixedly anchored to an arm mounting structure 31 which is positioned internally of the seat assembly 12. The arms 28 and 29 are each essentially of a one-piece construction, such as by being cast or otherwise suitably formed from a suitable material such as aluminum. Since arms 28 and 29 are identical, except for being mirror images of one another, only the arm 28 will be described in detail.

As illustrated by FIGS. 4-6, the arm 28 defines at its forward free end an arm rest portion 36 which extends approximately horizontally and, at its rearward end, is integrally joined to an intermediate portion 37 which is of a compound curvature in that as the portion 37 projects rearwardly, it also curves both downwardly and inwardly through angles of approximately 90°. This intermediate portion 37 terminates in a base portion 38 which is disposed at the rearward free end of the arm, which base portion 38 is positioned at the elevation of and substantially directly behind the rear edge of the seat assembly 12. The arm 28 preferably has a suitable padded arm rest 39 (FIG. 1) secured to the arm rest portion 36.

The arm base portion 38 has an armlike mounting portion 41 fixedly and integrally associated therewith, which mounting portion 41 projects forwardly toward the front edge of the chair seat. This armlike mounting portion 41 also slopes downwardly relative to the horizontal, such as at an angle Θ (FIG. 5) as it projects forwardly, which angle Θ is typically approximately 30°, although this angle could be as large as 45°. The elongated (that is, forwardly projecting) direction of the mounting portion 41 is such that when the two arms 28 and 29 are mounted on the chair, the mounting portions 41 associated with the two arms extend approximately in parallel relationship with one another.

Each mounting portion 41 includes an elongated mounting element 42 which is of a blocklike cross section and projects forwardly and downwardly from the base arm portion 38. A flange 43 is integrally associated with the mounting element 42 adjacent the free end thereof, which flange 43 projects upwardly from and extends transversely or sidewardly outwardly beyond the adjacent side of the element 42 in a direction toward the center of the seat assembly. The mounting element 42 and integral top flange 43 thus provide the mounting portion 41 with a substantially L-shaped configuration.

The mounting element 42 is preferably provided with opposite side walls 44 and 46 which are of a slight converging tapered relationship as they extend downwardly from top to bottom, which converging tapered relationship is preferably no more than a few degrees, for a purpose to be explained hereinafter.

The mounting portion 41 is also provided with three countersunk holes extending therethrough. One of these holes, namely hole 47, extends horizontally transversely through the element 42 adjacent the forward free end thereof, whereby this hole 47 thus extends between the opposed side surfaces 44 and 46. The second hole 48 extends downwardly from top to bottom through the portion 41 in the vicinity of the top flange 43, whereby this hole 48 is perpendicular to but spaced slightly rearwardly from the hole 47. The third hole 49 also extends downwardly through the portion 41 in parallel relationship to the hole 48, but is spaced rearwardly a substantial distance from the hole 48 so as to extend solely through the mounting element 42.

Considering now the mounting structure 31 as provided internally of the seat assembly, and as illustrated in FIGS. 2-3, same includes a U-shaped stretcher frame 51 which is formed in one piece from appropriate tubular cylindrical stock. This U-shaped tubular frame 51 includes parallel straight leg portions 52 which are positionable directly adjacent the chair-control frame rails 21. The stretcher legs 52 terminate at their rearward ends in rather large ninety-degree elbows 53 which are directed inwardly and are rigidly joined together by an intermediate straight bight 54. The U-shaped frame 51 is positioned within the seat assembly so that the frame opens forwardly, and hence the elbows 53 and bight 54 are thus positioned adjacent the rearward edge of the seat assembly. Each of the legs 52 adjacent the rearward end thereof (and substantially at the junction with the elbow 53) is provided with an upward bend 56. This bend 56 thus results in the elbows 53 and bight 54 being disposed with their centerlines lying within a plane which slopes upwardly and rearwardly at an angle Θ (FIG. 7) relative to the substantially horizontal plane defined by the longitudinally extending centerlines of the straight legs 52. This upwardly sloped position of the elbows 53 and bight 54 at the angle Θ is substantially the same as the downward slope of the arm mounting portions 41, which angle Θ in the illustrated embodiment is approximately 30°.

To fixedly secure the U-shaped stretcher frame 51 to the chair-control frame, each leg 52 has a pair of tabs 57 and 58 fixed thereto, such as by welding. These tabs 57-58 are located adjacent the opposite ends of the leg 52 and project sidewardly therefrom so as to directly overlie the adjacent support rail 21. The tabs have suitable openings 59 therethrough, and the support rail 21 has similar openings (not shown) thereunder, whereby suitable threaded fasteners project upwardly through the support rails 21 and through the tabs 58-59 into suitable threaded bosses formed on the underside of the inner support shell 17 so as to fixedly connect these elements together.

To attach the armlike mounting portion 41 to the U-shaped stretcher frame 51, the latter is provided with a pair of brackets 61 which are identical except for being mirror images of one another. The brackets are fixed to the pair of elbows 53 and project sidewardly therefrom toward the outer side edges of the seat assembly.

As shown in FIGS. 7-9, each bracket 61 is of an upwardly opening channel-like configuration, and includes a substantially planar base wall 62 which is substantially flush with and projects sidewardly from the underside of the elbow 53. This base wall 62 slopes upwardly at the same angle as the elbow, and is fixed to the elbow as by welding. The base wall 62 extends beneath the elbow and the inner edge thereof is bent upwardly through an angle of about 90° so as to form an inner flange 63, which inner flange is curved so as to conform to the inner curvature of the elbow, whereby the flange 63 is fixedly attached to the inner periphery of the elbow 53, as by welding. The outer side edge of the base wall 62 also has an integral outer flange 64 bent upwardly therefrom. This outer flange 64 is substantially planar and extends approximately parallel with but sidewardly offset from a vertical plane which contains therein the longitudinally extending axis of the straight leg 52.

The forward end of the base wall 62 is also bent upwardly to form a front flange 66. This flange 66 abuts and projects sidewardly from the tubular frame 51 so as to effectively close off the front end of the channel-like space 71 which is defined between the tube 51 and the outer flange 64. This latter flange 64 has its front edge 68 spaced rearwardly a substantial distance from the front flange 66, thereby providing a sidewardly directed opening into the channel 71, which opening hence provides access to an opening 67 (FIG. 7) as formed in the sidewall of the tube 51 substantially at the forward end of the elbow 53.

The bottom wall 62 of bracket 61 also has the rear portion thereof bent downwardly to form a strengthening or reinforcing flange 69. This bottom wall 62 also has an opening 72 formed therethrough at a location positioned in the vicinity of the front edge of flange 64, with a further identical such opening 73 also extending through the base wall at a location spaced rearwardly a substantial distance from the opening 72.

When the armlike mounting portion 41 is positioned within the bracket 61, an appropriate self-tapping screw 77 (FIG. 12) extends through the sideward opening 47 into the tube opening 67 for fixedly connecting the front or leading end of mounting portion 41 to the stretcher tube 51. Similar self-tapping screws 78-79 (FIGS. 11 and 13) extend downwardly through the openings 48-49 and respectively threadably engage the openings 72-73 formed in the base wall of the bracket for fixedly connecting the bracket and mounting portion together.

OPERATION

The structural and operational connection between the cantilevered arms 28-29 and the stretcher tube 51 as disposed internally of the seat assembly will be briefly described to insure a complete understanding thereof.

During assembly, the stretcher tube 51 is initially fixed to the rails 21 of the chair control by means of threaded fasteners which extend upwardly through openings in the rails 21 and through openings 59 in tabs 57-58, and then into the inner shell 17 for fixedly connecting both the tube 51 and the shell 17 to the chair-control frame. As secured the inner seat shell 17 is thus positioned above both the stretcher tube 51 and the chair control 16.

Thereafter the armlike mounting portion 41 of the cantilevered arm 28 is positioned within the channel 71 of the bracket 61. The portion 41 is disposed so that the front end of the mounting element 42 is disposed directly adjacent the front bracket flange 66, and the element 42 is tightly and wedgingly fitted between the tube 51 and the outer flange 64, substantially as illustrated by FIGS. 12 and 13. This tight fitting of the element 42, which results in the element being snugly sidewardly engaged with both the tube 51 and the flange 64, is normally insured by providing a slight wedging or tapered interfitting relationship. When snugly fit or wedged into position, the element 42 is substantially seated against the bracket base wall 62, and at the same time the projecting end of the top flange 43 directly overlies and is substantially seated against the upper surface of the tube 51. The self-tapping screw 77 is then inserted through the front hole 47 and is threadably tapped into the tube opening 67 so that screw 77 thus directly connects the element 42 to the tube 51 as shown in FIG. 12. The screw 78 is inserted through the hole 48 and is tappingly threaded into the opening 72 provided in the bracket base wall to thereby fixedly and snugly seat the element 42 against the bracket base wall in tightly wedged engagement between the tube 51 and the outer flange 64. The other screw 79 is similarly threaded into the other opening 73 associated with the bracket base wall. In this manner, the arm 28 is hence rigidly secured to the stretcher tube 51 in a very simple manner utilizing a relatively simple connecting structure, which structure occupies little space and can be easily fitted into the interior of the seat assembly, while at the same time this provides the cantilevered arm with substantial strength and rigidity so as to withstand the various direct forces and twisting or torsional moments imposed thereon.

For example, when a downwardly directed force is imposed against the arm rest portion 36 of the arm, such as a force F_(D) illustrated in FIG. 10, this force can be resolved into perpendicular components F_(C) and F_(T). The component F_(C) can be considered so as to act directly downwardly as a compression force which is transmitted by the mounting portion 41 directly against the stretcher tube 51, this force being imposed directly against the tube 51 by the top flange 43, or against the bracket base wall 62 by the mounting element 42. The other force component F_(T) is resisted by the bracket front flange 66, and creates a moment M_(T) which tends to tilt the arm 28 in a counterclockwise direction as illustrated in FIG. 10, so that the arm thus tends to rock about a pivot defined adjacent the lower front edge of the mounting portion 41. This moment M_(T) is hence primarily resisted by the rear screw 79, which screw has imposed thereon a tension force which, acting through a lever arm equal to the distance between the screw and the forward edge of the mounting portion 41, hence resists the twisting moment M_(T). Thus, this connecting structure, and specifically the fact that the bracket 61 and mounting portion 41 extend upwardly at the angle Θ, thus provides a very rigid and strong mounting of the cantilevered arm so that it can easily withstand the direct downward vertical force F_(D) while subjecting the mounting structure to forces of reasonable magnitude.

When a horizontally directed side force is imposed outwardly against the arm, which force would be directed perpendicularly outwardly in FIG. 5 and is represented by the point F_(S), this force is directly imposed against the outer bracket flange 64 and is also resisted by tension imposed on the sidewardly directed screw 77. This force F_(S), however, also creates a torsional moment M_(S) which tends to twist the mounting element 42 sidewardly within the bracket 61. This tendency for the mounting element 42 to twist, which occurs clockwise in FIGS. 12 and 13, is effectively resisted by the fact that this element 42 is tightly fit between the flange 64 and the tube 51, and thus a reactive moment is created by the tube 51 and flange 64 acting against the opposite sides of the mounting element 42 for resisting the moment M_(S).

The overall strength and rigidity provided by this mounting arrangement for the cantilevered arms 28 and 29 is accomplished by the provision of the simple U-shaped stretcher tube 51 inasmuch as the cantilevered arms have their mounting portions 41 disposed adjacent their rearward ends, with these mounting portions being directly fixedly attached to the brackets 61, which brackets are rigidly attached to the elbows 53 of the stretcher tube. These elbows 53 in turn are disposed adjacent the rear of the seat assembly, and the elbows themselves are directly and rigidly joined together by the intermediate tubular bight 54 which is also disposed adjacent the rear edge of the seat assembly. Hence, this bight 54 and associated elbows 53 effectively function as an integral rigid extension between the inner rear ends of the arms 28 and 29. Thus, even though this invention possesses the advantage of permitting the arms 28 and 29 to be constructed as separate individual elements, nevertheless the tubular bight 54 which is rigidly joined substantially directly between the rear inner ends of the arms 28-29 effectively permits the arms 28-29 to function as if they were formed as a single U-shaped structure, whereby the present invention thus possesses the advantages of such a single U-shaped arm structure, but not the obvious disadvantages thereof.

Although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention. 

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. In a chair having a seat assembly supported on a pedestal-type base, the seat assembly including a support structure positioned interiorly thereof, and a pair of cantilevered side arms positioned adjacent the opposite side edges of the seat assembly in upwardly spaced relationship therewith, comprising the improvement wherein:each said side arm is formed as a separate member and includes an arm rest portion at the front end thereof and a base portion at the rear end thereof, said base portion being positioned adjacent the rear edge of the seat assembly; said arm also including an elongated armlike mounting portion fixed to said base portion and projecting forwardly therefrom into the interior of said seat assembly; and mounting means fixed to said support structure and disposed within said seat assembly for fixedly but releasably supporting said cantilevered side arms; said mounting means including a frontwardly opening U-shaped frame member fixed to said support structure and having a bight portion disposed adjacent the rear edge of said seat assembly, said bight portion including a pair of sidewardly spaced elbows rigidly joined together by a substantially horizontally extending intermediate portion which extends sidewardly of the seat assembly, each said elbow having bracket means fixed thereto; said armlike mounting portion being fixedly but removably attached to one of said bracket means; and said U-shaped frame member including a pair of elongated and substantially straight legs which project toward the front edge of the seat assembly in substantially parallel relationship, said legs at their rearward ends being rigidly joined together by said bight portion, said legs extending approximately horizontally, said bight portion being bent upwardly relative to said legs as it projects rearwardly, and the mounting portion as fixed to each said arm being sloped downwardly as it projects forwardly from the base portion.
 2. A chair according to claim 1, wherein the elbows are rather smoothly bent through a gradual curvature of approximately 90° for joining the straight leg to the intermediate portion, each said elbow having a said bracket means fixed thereto and projecting sidewardly thereof, said bracket means cooperating with said elbow for defining an elongated rearwardly opening channel which projects toward the front of the seat assembly, and threaded fastener means for fixedly and rigidly connecting said mounting portion to said bracket means.
 3. A chair according to claim 1, wherein said bracket means includes a base wall which projects sidewardly from the underside of the elbow and slopes upwardly and rearwardly at the same angle as the bight portion, said bracket means also including an upwardly projecting side flange fixed to and projecting upwardly from the outer side edge of the base wall, said mounting portion being snugly positioned within the bracket means so that the opposite sides of the mounting portion are engaged with and between the elbow and the upwardly projecting side flange, and at least one said threaded fastener means projecting downwardly through the mounting portion adjacent the rearward end thereof for fixedly connecting the mounting portion to the base wall of the bracket means, and a second said threaded fastener means projecting downwardly through the mounting portion adjacent the forward end thereof for directly fixedly connecting the mounting portion to the base wall.
 4. A chair according to claim 3, wherein the bracket means includes a front flange which is fixed to and projects upwardly from the front edge of the base wall, said mounting portion having the free end thereof positioned adjacent said front flange.
 5. A chair according to claim 1, wherein the centerlines of the straight legs define a first plane which is approximately horizontal, and wherein the centerline of the bight portion defines a second plane which projects rearwardly and slopes upwardly relative to the horizontal at an angle which is at least approximately 25° and which does not significantly exceed 45°.
 6. A chair according to claim 1, wherein said armlike mounting portion includes an elongated blocklike arm member which projects forwardly from said base portion in cantilevered relationship therewith, said armlike mounting portion also including a top flange portion which is integrally fixed to the blocklike arm member adjacent the free end thereof and projects sidewardly inwardly therefrom, whereby the armlike mounting portion has a substantially L-shaped configuration, said top flange portion being adapted to overlie and bear against said elbow.
 7. A chair according to claim 3, wherein the centerlines of the straight legs define a first plane which is approximately horizontal, and wherein the centerline of the bight portion defines a second plane which projects rearwardly and slopes upwardly relative to the horizontal at an angle which is at least approximately 25° and which does not significantly exceed 45°.
 8. A chair according to claim 1, wherein said U-shaped frame member is formed from an elongated tube.
 9. A chair according to claim 2, wherein said U-shaped frame member is formed from an elongated tube.
 10. In a chair having a seat assembly supported on a base, the seat assembly including a support structure positioned interiorly thereof, and a pair of cantilevered side arms positioned adjacent the opposite side edges of the seat assembly in upwardly spaced relationship therewith, comprising the improvement wherein:each said side arm is formed as a separate member and includes an elongated arm rest portion at the front free end thereof, a base portion at the rear free end thereof, and a downwardly and sidewardly curved intermediate portion fixedly joined between said arm rest and base portions, said base portion being positioned downwardly, rearwardly and inwardly from said arm rest portion so as to be disposed adjacent the rear edge of the seat assembly; said side arm also including a cantilevered armlike mounting portion fixed to said base portion and projecting forwardly therefrom into the interior of said seat assembly; and mounting means fixed to said support structure and disposed within said seat assembly for fixedly but releasably supporting said cantilevered armlike mounting portions, said mounting means including a pair of bracket means disposed in sidewardly spaced relation within the interior of said seat assembly in the vicinity of the rear edge thereof, each said armlike mounting portion being fixedly but removably attached to one of said bracket means; each said bracket means comprising a rigid bracket defining therein a rearwardly extending channel which snugly accommodates said armlike mounting portion therein, and removable fastener means connected between said armlike mounting portion and said bracket for fixedly connecting same together.
 11. A chair according to claim 10, wherein said pair of bracket means are rigidly attached together by an elongate rigid intermediate tubular member which extends between the bracket means and is disposed closely adjacent the rear edge of the seat assembly.
 12. A chair according to claim 10, wherein said mounting means includes a U-shaped tubular frame member positioned within the interior of said seat assembly and fixedly secured to said support structure, said frame member having substantially parallel elongated side elements which are spaced sidewardly apart and are joined together by a bight portion which extends transversely therebetween, and said pair of bracket means being fixedly secured to said U-shaped frame member adjacent the opposite sides thereof.
 13. A chair according to claim 10, wherein said removable fastener means includes at least two threaded fasteners which rigidly connect each said armlike mounting portion to its respective said bracket, said fasteners extending predominantly in a vertical direction and being spaced apart in the rearward direction of the seat assembly.
 14. A chair according to claim 12, wherein the parallel elongated side elements are rigidly joined adjacent their front ends thereof to said support structure, and wherein said bight portion is disposed closely adjacent the rear edge of the seat assembly.
 15. In a chair having a seat assembly supported on a pedestal-type base, the seat assembly including an inner seat shell positioned interiorly therein, the seat assembly also including a support structure positioned interiorly thereof beneath said inner shell, and a pair of cantilevered side arms positioned adjacent the opposite side edges of the seat assembly in upwardly spaced relationship therewith, comprising the improvement wherein:each said side arm is formed as a separate member and includes an arm rest portion at the front end thereof and a base portion at the rear end thereof; said arm also including an elongated armlike mounting portion fixed to said base portion and projecting therefrom into the interior of said seat assembly; and mounting means fixed to said support structure and disposed within said seat assembly for fixedly but releasably supporting said cantilevered arms; said mounting means including a one-piece U-shaped tubular frame member positioned within the interior of said seat assembly below said inner shell and fixedly secured to said support structure, said frame member having substantially parallel elongated side elements which are spaced sidewardly apart and are joined together by a bight portion which extends transversely therebetween, said side elements being rigidly secured to said support strucure, and a pair of channellike bracket means fixedly secured to said U-shaped frame member adjacent the opposite sides thereof; and each said armlike mounting portion being positioned in and fixedly but removably attached to a respective one of said channellike bracket means.
 16. A chair according to claim 15, wherein said channellike bracket means open rearwardly, and removable fastener means connected between said armlike mounting portion and said bracket means for fixedly connecting same together, said removable fastener means including a pair of threaded fasteners which are rearwardly spaced apart and project substantially vertically for joining said armlike mounting portion and the respective said bracket means together. 